fmt: deno fmt - formats stdin and print to stdout

[kevinkassimo]

Closes #3877

Add --stdin flag (also compatible with --check) to format stdin input

deno fmt - now reads from stdin and prints output to stdout.

$ echo "const    a=1" | ./target/debug/deno fmt -
const a = 1;

[nayeemrmn]

I think it's common to use - in place of the file name to represent reading from stdin / writing to stdout.

[kevinkassimo]

@nayeemrmn That’s also an option. Love to get more feedback also from others

[dplewis]

How about without the flag? If no files input then read from pipe?

[axetroy]

@dplewis

agree. see what I wrote before

deno/std/prettier/main.ts

Lines 548 to 564 in 8bc639a

	const tty = Deno.isTTY();
	const shouldReadFromStdin =
	(!tty.stdin && (tty.stdout || tty.stderr)) || !!opts["stdin"];
	try {
	if (shouldReadFromStdin) {
	await formatFromStdin(opts["stdin-parser"], prettierOpts);
	} else if (check) {
	await checkSourceFiles(files, prettierOpts);
	} else {
	await formatSourceFiles(files, prettierOpts);
	}
	} catch (e) {
	console.error(e);
	exit(1);
	}

[nayeemrmn]

How about without the flag? If no files input then read from pipe?

Hmm, we may want to have a default glob for this case.

[kevinkassimo]

@dplewis Currently if we don't have any arguments, we implicitly push **/*

deno/cli/fmt.rs

Line 162 in f650c3e

let glob_paths = maybe_files.unwrap_or_else(|| vec!["**/*".to_string()]);

[dplewis]

Sorry I'm a beginner at rust 😅If there are no arguments couldn't you check stdin().lines() first before pushing **/*?

The flag is fine too.

[bartlomieju]

It looks like besides reading from stdin it outputs code to stdout. Can you describe this behavior in help text? (Maybe add an example to subcommand as well)

[nayeemrmn]

This is another reason - would be better. The meaning of this functionality is specifically "stdin/stdout". This is conventionally represented with -, whereas --stdin is misleading. I feel more strongly about it now.

[kevinkassimo]

@nayeemrmn - can be a valid filename. (nah I'm just joking + bikeshedding here)

Yeah --stdin is a bit long to type and its implicit effect on stdout is definitely slightly confusing... If @bartlomieju also thinks - is better then it is a very easy change to make.

[bartlomieju]

Yeah, SGTM, if that's an easy change I guess it makes more sense - we already have similar argument in catj.

[bartlomieju]

@dplewis Currently if we don't have any arguments, we implicitly push **/*

deno/cli/fmt.rs

Line 162 in f650c3e

let glob_paths = maybe_files.unwrap_or_else(|| vec!["**/*".to_string()]);

@ry and I had a talk about it - we're not happy with current glob solution and are thinking about removing it entirely for now. Glob crates available in Rust have completely different functionality (and it seems syntax too) than std/globrex that we used before.

[bartlomieju]

LGTM, one nitpick